Not necessary to dig through poop. One seed is not poisonous, in order to ingest a potentially dangerous amount you would have to purposely collect the pits, crack them, eat the insides (not by swallowing whole but by chewing them well) and eat too much at once, or too many for your body size throughout the day. It is said if you eat the raw fruit (in this case the cherry) along with the pit, it helps detoxify the cyanide. You need to be more careful if you're planning on eating the pits without their accompanying fruit. People for many years have been swallowing fruits, along with their seeds, and not dropping dead like flies. It is true it would take a smaller amount to affect a toddler but I certainly wouldn't worry about one seed. Some people purposely ingest apricot kernels and seeds from other fruits for the vitamin B17 it is said to kill cancer and there have been many people eating a lot of seeds to no ill effect. I think it is around 2 to 5 seeds per hour, depending upon your body weight. This is in reference to the apricot, which is MUCH higher than a cherry pit. TOO much IS a poison yes, but for that matter, so is water. (too much water too fast can also kill you) I think there was only ONE documented case of someone dying from seeds, I believe they ate more than a CUP of apple seeds, can you imagine how many apples it would have taken to collect that many? It is said do not eat more seeds than you would normally be able to eat of the accompanying fruits, and you'd be fine. The powers that be repeat the death case over and over to illustrate the fact that seeds are poisonous and as a result people think that a few seeds are bad, they want to scare you away from the idea for whatever reasons but seeds in very small amounts are just fine and from the research I have done are also quite beneficial. (and I've ingested my share of seeds in the past, and am still here)
Don't worry Mama, she's fine

"All that is necessary for the triumph of evil is that good men do nothing." -Edmund Burke (1729-1797)